Abstract
We reported a controllable way of removing excess Fe in Fe1+yTe0.6Se0.4 by annealing in a fixed amount of O2. Compared with the weak superconductivity induced by dilute acids, O2 annealing can successfully induce bulk superconductivity. Proper O2 annealing changes the temperature dependence of resistivity at low temperatures from semiconducting to metallic, which comes from the deintercalation of excess Fe. Critical current densities with field along the c-axis and ab-plane are found almost isotropic with large values of JcH∥c∼3×105 A/cm2 and JcH∥ab∼2.5×105 A/cm2 at 2 K. Furthermore, magneto-optical images reveal isotropic current flow within the ab-plane.